[src/chs-ubc2]: src/sys/ufs/ufs in ufs_balloc_range(), read any partial pages...

[chs <chs%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0d6c31e0f872
branches:  chs-ubc2
changeset: 471394:0d6c31e0f872
user:      chs <chs%NetBSD.org@localhost>
date:      Sun Jul 11 05:51:40 1999 +0000

description:
in ufs_balloc_range(), read any partial pages that were already
allocated before allocating additional blocks in the same page.
hold these pages busy for the duration of the allocations and
release them when we're done.

diffstat:

 sys/ufs/ufs/ufs_inode.c |  100 ++++++++++++++++++++++++++++++++++++++++++++---
 1 files changed, 93 insertions(+), 7 deletions(-)

diffs (156 lines):

diff -r c5941024d56a -r 0d6c31e0f872 sys/ufs/ufs/ufs_inode.c
--- a/sys/ufs/ufs/ufs_inode.c   Sun Jul 11 05:49:07 1999 +0000
+++ b/sys/ufs/ufs/ufs_inode.c   Sun Jul 11 05:51:40 1999 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ufs_inode.c,v 1.13.4.1 1999/07/04 01:54:31 chs Exp $   */
+/*     $NetBSD: ufs_inode.c,v 1.13.4.2 1999/07/11 05:51:40 chs Exp $   */
 
 /*
  * Copyright (c) 1991, 1993
@@ -55,6 +55,8 @@
 #include <ufs/ufs/ufsmount.h>
 #include <ufs/ufs/ufs_extern.h>
 
+#include <uvm/uvm.h>
+
 /*
  * Last reference to an inode.  If necessary, write or delete it.
  */
@@ -148,7 +150,10 @@
 }
 
 /*
- * Allocate a range of blocks in a file.
+ * allocate a range of blocks in a file.
+ * after this function returns, any page entirely contained within the range
+ * will map to invalid data and thus must be overwritten before it is made
+ * accessible to others.
  */
 
 int
@@ -158,13 +163,60 @@
        struct ucred *cred;
        int flags;
 {
+       off_t pagestart, pageend;
+       struct uvm_object *uobj = &vp->v_uvm.u_obj;
        struct inode *ip = VTOI(vp);
        int bshift, bsize, delta, error;
+       struct vm_page *pg1, *pg2;
+       int npages;
+       UVMHIST_FUNC("ufs_balloc_range"); UVMHIST_CALLED(ubchist);
+
+       UVMHIST_LOG(ubchist, "vp %p off 0x%x len 0x%x u_size 0x%x",
+                   vp, (int)off, (int)len, (int)vp->v_uvm.u_size);
 
        bshift = vp->v_mount->mnt_fs_bshift;
        bsize = 1 << bshift;
 
        /*
+        * if the range does not start on a page boundary,
+        * cache the first page if the file so the page will contain
+        * the correct data.  hold the page busy while we allocate
+        * the backing store for the range.
+        */
+
+       error = 0;
+       pg1 = pg2 = NULL;
+       pagestart = trunc_page(off);
+       if (off != pagestart && pagestart < ip->i_ffs_size) {
+               npages = 1;
+               simple_lock(&uobj->vmobjlock);
+               error = VOP_GETPAGES(vp, pagestart, &pg1, &npages, 0,
+                                    VM_PROT_READ, 0, PGO_SYNCIO);
+               if (error) {
+                       goto errout;
+               }
+               UVMHIST_LOG(ubchist, "got first pg %p", pg1,0,0,0);
+       }
+
+       /*
+        * similarly if the range does not end on a page boundary.
+        */
+
+       pageend = trunc_page(off + len);
+       if (off + len != pageend && pagestart != pageend &&
+           pageend < ip->i_ffs_size) {
+               npages = 1;
+               simple_lock(&uobj->vmobjlock);
+               error = VOP_GETPAGES(vp, pageend, &pg2, &npages, 0,
+                                    VM_PROT_READ, 0, PGO_SYNCIO);
+               if (error) {
+                       goto errout;
+               }
+               UVMHIST_LOG(ubchist, "got second pg %p",
+                           pg2, (int)(off + len), (int)ip->i_ffs_size,0);
+       }
+
+       /*
         * adjust off to be block-aligned.
         */
 
@@ -173,19 +225,19 @@
        len += delta;
 
        /*
-        * allocate the range a block at a time.
+        * now allocate the range a block at a time.
         */
 
        while (len > 0) {
                bsize = min(bsize, len);
 
                if ((error = VOP_BALLOC(vp, off, bsize, cred, flags, NULL))) {
-                       return error;
+                       goto errout;
                }
 
                /*
-                * increase file size now.
-                * ffs_balloc() needs to know in the case where we loop here.
+                * increase file size now, VOP_BALLOC() requires that
+                * EOF be up-to-date before each call.
                 */
 
                if (ip->i_ffs_size < off + bsize) {
@@ -196,5 +248,39 @@
                len -= bsize;
                off += bsize;
        }
-       return 0;
+
+       /*
+        * unbusy any pages we are holding.
+        */
+
+errout:
+       simple_lock(&uobj->vmobjlock);
+       if (pg1 != NULL) {
+               if (pg1->flags & PG_WANTED) {
+                       wakeup(pg1);
+               }
+               if (pg1->flags & PG_RELEASED) {
+                       UVMHIST_LOG(ubchist, "releasing pg %p", pg1,0,0,0);
+                       uobj->pgops->pgo_releasepg(pg1, NULL);
+               } else {
+                       UVMHIST_LOG(ubchist, "unbusing pg %p", pg1,0,0,0);
+                       pg1->flags &= ~(PG_WANTED|PG_BUSY);
+                       UVM_PAGE_OWN(pg1, NULL);
+               }
+       }
+       if (pg2 != NULL) {
+               if (pg2->flags & PG_WANTED) {
+                       wakeup(pg2);
+               }
+               if (pg2->flags & PG_RELEASED) {
+                       UVMHIST_LOG(ubchist, "releasing pg %p", pg2,0,0,0);
+                       uobj->pgops->pgo_releasepg(pg2, NULL);
+               } else {
+                       UVMHIST_LOG(ubchist, "unbusing pg %p", pg2,0,0,0);
+                       pg2->flags &= ~(PG_WANTED|PG_BUSY);
+                       UVM_PAGE_OWN(pg2, NULL);
+               }
+       }
+       simple_unlock(&uobj->vmobjlock);
+       return error;
 }